133O - Extended adjuvant aromatase inhibition after sequential endocrine therapy: Final results of the phase III DATA trial

Background

The DATA study evaluated the use of different durations of anastrozole in patients with hormone receptor-positive breast cancer who were disease-free after 2-3 years of tamoxifen. Here, we present the final analysis.

Methods

The DATA study was a phase III, open-label, randomised controlled trial performed in 79 hospitals in the Netherlands. Postmenopausal women with hormone receptor-positive breast cancer who were disease-free after 2-3 years of adjuvant tamoxifen received either 3 or 6 years of anastrozole in a 1:1 ratio. Randomisation was stratified by nodal status, hormone receptor status, HER2 status and duration of prior tamoxifen treatment. The primary endpoint was adapted disease-free survival (aDFS), defined as DFS from 3 years after randomisation onwards. Adapted overall survival (aOS) was evaluated as a secondary endpoint.

Results

Between June 2006 and August 2009, 1912 patients were randomly assigned to 3 or 6 years of anastrozole. Of these, 1660 patients were eligible and disease-free at 3 years after randomisation. The median adapted follow-up time was 10.1 years. The 10-year aDFS was 69% (95% confidence interval (CI): 66%-72%) in the 6-year group and 66% (95% CI: 63%-69%) in the 3-year group (hazard ratio 0.86; 95% CI: 0.72-1.01; p=0.073), with no difference in aOS (hazard ratio 0.93; 95% CI: 0.75-1.16; p=0.53). The effect of extended treatment on aDFS differed between patients with tumours expressing both oestrogen receptors (ER) and progesterone receptors (PR) (hazard ratio 0.77; 95% CI: 0.63-0.94; p=0.008), and patients with tumours expressing only one receptor (hazard ratio 1.22; 95% CI: 0.86-1.73; p=0.28) (p interaction=0.018). In patients with node-positive, ER- and PR-positive tumours (n=849), the 10-year aDFS was 69% (95% CI: 64%-73%) in the 6-year group and 61% (95% CI: 56%-65%) in the 3-year group (hazard ratio 0.74; 95% CI: 0.59-0.93; p=0.011), with no significant difference in aOS (hazard ratio 0.84; 95% CI: 0.62-1.12; p=0.23).

Conclusions

We cannot recommend extending aromatase inhibition beyond 5 years of sequential therapy in all postmenopausal women with hormone receptor-positive breast cancer. It may however be considered in patients with node-positive, ER- and PR-positive tumours.

Clinical trial identification

NCT00301457.

Editorial acknowledgement

Legal entity responsible for the study

Maastricht UMC+.

Funding

AstraZeneca.

Disclosure

V.C.G. Tjan-Heijnen: Financial Interests, Institutional, Research Grant: AstraZeneca, Roche, Novartis, Eli Lilly, Pfizer, Eisai, Daiichi Sankyo, Gilead; Financial Interests, Personal, Advisory Role: Pfizer, Eli Lilly, Accord, Novartis; Financial Interests, Personal, Other, Honorarium: Novartis, Roche, Eli Lilly, AstraZeneca. S.W.M. Lammers: Financial Interests, Institutional, Research Grant: AstraZeneca. S.M.E. Geurts: Financial Interests, Institutional, Research Grant: AstraZeneca, Roche, Pfizer, Novartis, Eli Lilly, Daiichi Sankyo, Gilead; Financial Interests, Personal, Advisory Board: AstraZeneca. I.J.H. Vriens: Financial Interests, Institutional, Research Grant: AstraZeneca, Pfizer; Financial Interests, Personal, Advisory Board: Pfizer, Novartis. A.C.P. Swinkels: Financial Interests, Institutional, Research Grant: AstraZeneca. J.R. Kroep: Financial Interests, Institutional, Research Grant: AstraZeneca, Novartis, Philips. A.H. Honkoop: Financial Interests, Institutional, Research Grant: Dutch Breast Cancer Research Group; Financial Interests, Personal, Advisory Board: Eli Lilly. S.C. Linn: Financial Interests, Institutional, Advisory Board: AstraZeneca, Cergentis, IBM, Novartis, Pfizer, Roche, Sanofi; Financial Interests, Institutional, Research Grant: Agendia, Amgen, AstraZeneca, Eurocept Pharmaceuticals, Genentech, Immunomedics, Merck, Roche, Sanofi, TESARO; Financial Interests, Institutional, Funding: Bayer, Daiichi Sankyo; Other, Institutional, Ownership Interest, Patent application: BRCA-like ovarian cancer classifier. A.L.T. Imholz: Financial Interests, Institutional, Research Grant: AstraZeneca. All other authors have declared no conflicts of interest.